Atoms

24 pages, 1450 KiB

Open AccessArticle

Introducing Machine Learning in Teaching Quantum Mechanics

by M. K. Pawelkiewicz, Filippo Gatti, Didier Clouteau, Viatcheslav Kokoouline and Mehdi Adrien Ayouz

Atoms 2025, 13(7), 66; https://doi.org/10.3390/atoms13070066 - 8 Jul 2025

Abstract

In this article, we describe an approach to teaching introductory quantum mechanics and machine learning techniques. This approach combines several key concepts from both fields. Specifically, it demonstrates solving the Schrödinger equation using the discrete-variable representation (DVR) technique, as well as the architecture [...] Read more.

In this article, we describe an approach to teaching introductory quantum mechanics and machine learning techniques. This approach combines several key concepts from both fields. Specifically, it demonstrates solving the Schrödinger equation using the discrete-variable representation (DVR) technique, as well as the architecture and training of neural network models. To illustrate this approach, a Python-based Jupyter notebook is developed. This notebook can be used for self-learning or for learning with an instructor. Furthermore, it can serve as a toolbox for demonstrating individual concepts in quantum mechanics and machine learning and for conducting small research projects in these areas. Full article

(This article belongs to the Special Issue Artificial Intelligence for Quantum Sciences)

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10 pages, 14429 KiB

Open AccessArticle

Polarization Reconstruction Based on Monte Carlo Simulations for a Compton Polarimeter

by Tobias Over-Winter, Wilko Middents, Günter Weber and Thomas Stöhlker

Atoms 2025, 13(7), 65; https://doi.org/10.3390/atoms13070065 - 4 Jul 2025

Abstract

State-of-the-art 2D sensitive semiconductor detectors developed within the SPARC collaboration can be utilized as dedicated Compton polarimeters in the hard X-ray regime. We report on the technique of Compton polarimetry utilizing such a detector and present a method to determine the linear polarization [...] Read more.

State-of-the-art 2D sensitive semiconductor detectors developed within the SPARC collaboration can be utilized as dedicated Compton polarimeters in the hard X-ray regime. We report on the technique of Compton polarimetry utilizing such a detector and present a method to determine the linear polarization of an analyzed hard X-ray beam by means of Monte-Carlo-simulated data sets. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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13 pages, 398 KiB

Open AccessArticle

Electron Impact Ionization and Partial Ionization Cross Sections of Plasma-Relevant SiCl_x (x = 1–3) Molecules

by Savinder Kaur, Ajay Kumar Arora, Kasturi Lal Baluja and Anand Bharadvaja

Atoms 2025, 13(7), 64; https://doi.org/10.3390/atoms13070064 - 3 Jul 2025

Abstract

The electron-impact ionization and partial ionization cross sections are reported for few silicon-chlorine molecules using semi-empirical methods. The partial ionization cross sections are determined using a modified version of the binary-encounter-Bethe model. In this approach, the binary-encounter-Bethe model is modified through a two-step [...] Read more.

The electron-impact ionization and partial ionization cross sections are reported for few silicon-chlorine molecules using semi-empirical methods. The partial ionization cross sections are determined using a modified version of the binary-encounter-Bethe model. In this approach, the binary-encounter-Bethe model is modified through a two-step process, namely, transforming the binding energies of the occupied orbitals and introducing a scaling factor. The scaling can be done using either the mass spectrometry data or experimental values of cross sections. It correctly adjusts the scaling term of the BEB model so that the order of magnitude of resulting partial ionization cross sections is the same as that of experimental values. Further, the use of the experimental value of ionization and appearance energy values ensures that the cross sections have a correct threshold. This further mitigates the dependence of cross sections on energy at low values. The role of the scaling factor and the behavior of branching ratios is also examined at different energies. The species whose partial ionization cross sections are reported are highly relevant in plasma processing. However, the proposed model can be extended to any multi-centerd molecular structures comprising a large number of atoms or electrons, except in cases where resonance effects or additional ionization channels become significant. The mass spectrometry data is of utmost importance in computing partial ionization cross sections in order to obtain reliable results. Full article

(This article belongs to the Special Issue Electron-Impact Ionization: Fragmentation and Cross-Section)

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18 pages, 433 KiB

Open AccessArticle

Controlling the Ionization Dynamics of Argon Induced by Intense Laser Fields: From the Infrared Regime to the Two-Color Configuration

by Soumia Chqondi, Souhaila Chaddou, Ahmad Laghdas and Abdelkader Makhoute

Atoms 2025, 13(7), 63; https://doi.org/10.3390/atoms13070063 - 1 Jul 2025

Abstract

The current study presents the results of a methodical investigation into the ionization of rare gas atoms, specifically focusing on argon. In this study, two configurations are examined: ionization via a near-infrared (NIR) laser field alone, and ionization caused by extreme ultraviolet (XUV) [...] Read more.

The current study presents the results of a methodical investigation into the ionization of rare gas atoms, specifically focusing on argon. In this study, two configurations are examined: ionization via a near-infrared (NIR) laser field alone, and ionization caused by extreme ultraviolet (XUV) radiation in the presence of a strong, synchronized NIR pulse. The theoretical investigation is conducted using an ab initio method to solve the time-dependent Schrödinger equation within the single active electron (SAE) approximation. The simulation results show a sequence of above-threshold ionization (ATI) peaks that shift to lower energies with increasing laser intensity. This behavior reflects the onset of the Stark effect, which modifies atomic energy levels and increases the number of photons required for ionization. An examination of the two-color photoionization spectrum, which includes sideband structures and harmonic peaks, shows how the ionization probability is redistributed between the direct path (single XUV photon absorption) and sideband pathways (XUV ± n × IR) as the intensity of the infrared field increases. Quantum interference between continuum states is further revealed by the photoelectron angular distribution, clearly indicating the control of ionization dynamics by the IR field. Full article

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19 pages, 764 KiB

Open AccessArticle

Subradiance Generation in a Chain of Two-Level Atoms with a Single Excitation

by Nicola Piovella

Atoms 2025, 13(7), 62; https://doi.org/10.3390/atoms13070062 - 1 Jul 2025

Abstract

Studies of subradiance in a chain N two-level atoms in the single excitation regime focused mainly on the complex spectrum of the effective Hamiltonian, identifying subradiant eigenvalues. This can be achieved by finding the eigenvalues N of the Hamiltonian or by evaluating the [...] Read more.

Studies of subradiance in a chain N two-level atoms in the single excitation regime focused mainly on the complex spectrum of the effective Hamiltonian, identifying subradiant eigenvalues. This can be achieved by finding the eigenvalues N of the Hamiltonian or by evaluating the expectation value of the Hamiltonian on a generalized Dicke state, depending on a continuous variable k. This has the advantage that the sum above N can be calculated exactly, such that N becomes a simple parameter of the system and no longer the size of the Hilbert space. However, the question remains how subradiance emerges from atoms initially excited or driven by a laser. Here we study the dynamics of the system, solving the coupled-dipole equations for N atoms and evaluating the probability to be in a generalized Dicke state at a given time. Once the subradiant regions have been identified, it is simple to see if subradiance is being generated. We discuss different initial excitation conditions that lead to subradiance and the case of atoms excited by switching on and off a weak laser. This may be relevant for future experiments aimed at detecting subradiance in ordered systems. Full article

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21 pages, 964 KiB

Open AccessArticle

Curvature Effects on the Regimes of the Lateral van der Waals Force

by Alexandre P. Costa, Lucas Queiroz and Danilo T. Alves

Atoms 2025, 13(7), 61; https://doi.org/10.3390/atoms13070061 - 25 Jun 2025

Abstract

Recently, it has been shown that, under the action of the lateral van der Waals (vdW) force due to a perfectly conducting corrugated plane, a neutral anisotropic polarizable particle in vacuum can be attracted not only to the nearest corrugation peak but also [...] Read more.

Recently, it has been shown that, under the action of the lateral van der Waals (vdW) force due to a perfectly conducting corrugated plane, a neutral anisotropic polarizable particle in vacuum can be attracted not only to the nearest corrugation peak but also to a valley or an intermediate point between a peak and a valley, with such behaviors called peak, valley, and intermediate regimes, respectively. In the present paper, we discuss how the curvature of the corrugated surface affects the occurrence of the mentioned regimes. For this, we calculate the vdW interaction between a polarizable particle and a grounded conducting corrugated cylinder. We consider the corrugations along the azimuthal (

ϕ

-direction) angle or along the cylinder axis (z-direction). We show that when the corrugation occurs in the z-direction, the curvature has a small effect on the occurrence of the valley regime. On the other hand, it inhibits the intermediate regimes up to a certain particle–surface distance above which it amplifies the occurrence of this regime. When the corrugation occurs in the

ϕ

-direction, we show that the curvature inhibits both the valley and intermediate regimes. Full article

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18 pages, 332 KiB

Open AccessArticle

Hydrogenic Matrix Elements with Different Effective Charges: Non-Relativistic and Relativistic Cases

by Héctor O. Di Rocco and Julio C. Aguiar

Atoms 2025, 13(7), 60; https://doi.org/10.3390/atoms13070060 - 20 Jun 2025

Abstract

This work explores the evaluation of hydrogenic matrix elements for non-relativistic and relativistic cases under the Screened Hydrogenic Model (SHM). It focuses on scenarios where the initial and final states have different effective charges

Z_{1} \neq Z_{2}

, deriving closed-form solutions [...] Read more.

This work explores the evaluation of hydrogenic matrix elements for non-relativistic and relativistic cases under the Screened Hydrogenic Model (SHM). It focuses on scenarios where the initial and final states have different effective charges

Z_{1} \neq Z_{2}

, deriving closed-form solutions for particular cases

n_{1} = n_{2}

and

Z_{1} = Z_{2}

. In addition, analytical expressions for radial matrix elements

⟨ n^{'} l^{'} | r^{β} | n l ⟩

and their relativistic counterparts are presented. These are applicable for discrete–discrete transitions and allow simplifications for specific configurations using Laplace transforms. The study discusses generalizations of SHM for calculating cross-sections in hot and dense plasmas, employing the Plane Wave Born Approximation (PWBA). It also addresses the transition from LS to jj coupling for matrix elements, providing rules for such transformations. Full article

(This article belongs to the Special Issue Atom and Plasma Spectroscopy)

9 pages, 533 KiB

Open AccessArticle

Comparison of Different Rydberg Atom-Based Microwave Electrometry Techniques

by Eliel Leandro Alves Junior, Manuel Alejandro Lefrán Torres, Jorge Douglas Massayuki Kondo and Luis Gustavo Marcassa

Atoms 2025, 13(7), 59; https://doi.org/10.3390/atoms13070059 - 20 Jun 2025

Abstract

In this study, we have compared different Rydberg atom-based microwave electrometry techniques under the same experimental conditions and using the same Rydberg states (

68 S_{1 / 2}

,

68 P_{3 / 2}

, and

67 P_{3 / 2}

). [...] Read more.

In this study, we have compared different Rydberg atom-based microwave electrometry techniques under the same experimental conditions and using the same Rydberg states (

68 S_{1 / 2}

,

68 P_{3 / 2}

, and

67 P_{3 / 2}

). The comparison was carried out for the following techniques: (i) auxiliary microwave field, (ii) microwave amplitude modulation, and (iii) polarization spectroscopy. Our results indicate that all three techniques have a similar minimum measurable microwave electric field. A slightly better result can be obtained by performing polarization spectroscopy using a Laguerre–Gauss coupling laser beam. Full article

(This article belongs to the Section Atom Based Quantum Technology)

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12 pages, 819 KiB

Open AccessArticle

Ionization of CF₃CH₂F by Protons and Photons

by Carlos E. Ferreira, Jorge A. de Souza-Corrêa, Alexandre B. Rocha and Antônio C. F. Santos

Atoms 2025, 13(6), 58; https://doi.org/10.3390/atoms13060058 - 18 Jun 2025

Abstract

(1) Background: Ionizing radiation in the Earth’s atmosphere drives key chemical transformations affecting atmospheric composition. Despite their environmental relevance, experimental data on proton collisions with hydrofluorocarbons remain limited, and theoretical models for total cross-sections and stopping power are still underdeveloped. (2) Methods: This [...] Read more.

(1) Background: Ionizing radiation in the Earth’s atmosphere drives key chemical transformations affecting atmospheric composition. Despite their environmental relevance, experimental data on proton collisions with hydrofluorocarbons remain limited, and theoretical models for total cross-sections and stopping power are still underdeveloped. (2) Methods: This study applies Rudd’s semiempirical model to calculate proton impact ionization cross-sections for the CF₃CH₂F molecule, considering contributions from both outer and inner electron shells. The model enables the estimation of differential cross-sections and the average energy of secondary electrons. In addition, we calculate the photoionization cross-sections using a discretized representation of the continuum—the so-called pseudo-spectrum—obtained through TDDFT with PBE0 as an exchange–correlation functional and compare it with the cross-section obtained for proton impact in the high-energy limit. (3) Results: The Rudd model proves highly adaptable and suitable for numerical applications. However, its validation is hindered by the scarcity of experimental data. Existing models, such as SRIM and Bethe–Bloch, show significant discrepancies due to their limited applicability at intermediate energies and lack of molecular structure consideration. (4) Conclusions: A comparison between the Rudd and BEB models reveals strong agreement in the analyzed energy range. This consistency stems from both models accounting for the molecular structure of the target, as well as from the fact that protons and electrons possess charges of the same magnitude, supporting a coherent description of ionization processes at these energies. Full article

(This article belongs to the Special Issue Electronic, Photonic and Ionic Interactions with Atoms and Molecules)

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19 pages, 857 KiB

Open AccessArticle

An Explicit Numerical Scheme for Milne’s Phase–Amplitude Equations

by Robin Piron and Mikael Tacu

Atoms 2025, 13(6), 57; https://doi.org/10.3390/atoms13060057 - 18 Jun 2025

Abstract

We present an explicit numerical method to solve Milne’s phase–amplitude equations. Existing methods directly solve Milne’s nonlinear equation for amplitude. For that reason, they exhibit high sensitivity to errors and are prone to instability through the growth of a spurious, rapidly varying component [...] Read more.

We present an explicit numerical method to solve Milne’s phase–amplitude equations. Existing methods directly solve Milne’s nonlinear equation for amplitude. For that reason, they exhibit high sensitivity to errors and are prone to instability through the growth of a spurious, rapidly varying component of the amplitude. This makes the systematic use of these methods difficult. On the contrary, the present method is based on solving a linear third-order equation which is equivalent to the nonlinear amplitude equation. This linear equation was derived by Kiyokawa, who used it to obtain analytical results on Coulomb wavefunctions. The present method uses this linear equation for numerical computation, thus resolving the problem of the growth of a rapidly varying component. Full article

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14 pages, 2874 KiB

Open AccessArticle

Quantitative Analysis of Lithium in Natural Brines from the Lithium Triangle by Laser-Induced Breakdown Spectroscopy

by Juan Molina M., Carisa Sarchi, Alvaro Y. Tesio, César Costa-Vera and Diego M. Díaz Pace

Atoms 2025, 13(6), 56; https://doi.org/10.3390/atoms13060056 - 17 Jun 2025

Abstract

Lithium (Li)-rich continental brines found in the Lithium Triangle region in South America are a natural resource of paramount importance. In the present research, the analytical performance of laser-induced breakdown spectroscopy (LIBS) technology was assessed for the quantitative analysis of Li in natural [...] Read more.

Lithium (Li)-rich continental brines found in the Lithium Triangle region in South America are a natural resource of paramount importance. In the present research, the analytical performance of laser-induced breakdown spectroscopy (LIBS) technology was assessed for the quantitative analysis of Li in natural brines aimed at enhancing the efficient exploration of salt flats (called salars). Brine samples were collected from different salars located in the Puna plateau (Northwest Argentina) and analyzed by LIBS in the form of solid pressed pellets. Broadband emission spectra (180–900 nm) were recorded and spectrally analyzed by specially designed computational algorithms. The laser-induced plasmas were characterized by calculating the electron density and the temperature. The Li elemental concentrations in the brines were determined through univariate calibration with the Li I emission line at 670.77 nm by using a suitable set of standards with Li concentrations up to 1300

μ

g/g. The calculated limit of detection was LoD = 0.2 ± 0.1

μ

g/g. The Li content in the brines determined with LIBS showed a good agreement (normalized standard deviation: σ_N = 25%) with the concentrations measured with atomic absorption spectroscopy. The results demonstrated the feasibility of the LIBS technique for the quantitative analysis of Li in natural brines, thus contributing to advancing the exploration of Li-rich resources. Full article

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Graphical abstract

8 pages, 360 KiB

Open AccessObituary

Nigel R. Badnell (1958–2024): A Legacy in Atomic Astrophysics

by Giulio Del Zanna, Helen E. Mason, Peter J. Storey, Stefan Kuhr, Chunyu Zhang, Junjie Mao, Gary J. Ferland, Alessandra Giunta and Roger P. Dufresne

Atoms 2025, 13(6), 55; https://doi.org/10.3390/atoms13060055 - 17 Jun 2025

Abstract

Nigel Robert Badnell was born on the 27th of October 1958 and grew up in Swindon where he lived with his parents, Dave and Patricia, and his wee sister, Hilary [...] Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

15 pages, 875 KiB

Open AccessArticle

Multi-Configuration Dirac–Hartree–Fock Calculations of Pr⁹⁺ and Nd¹⁰⁺: Configuration Resolution and Probing Fine-Structure Constant Variation

by Songya Zhang, Cunqiang Wu, Chenzhong Dong and Xiaobin Ding

Atoms 2025, 13(6), 54; https://doi.org/10.3390/atoms13060054 - 16 Jun 2025

Abstract

We present high-precision multi-configuration Dirac–Hartree–Fock (MCDHF) calculations for the metastable states of

\Pr^{9 +}

and

{Nd}^{10 +}

ions, systematically investigating their energy levels, transition properties, Landé

g_{J}

factors, and hyperfine interaction constants. Our results show excellent agreement with available experimental [...] Read more.

We present high-precision multi-configuration Dirac–Hartree–Fock (MCDHF) calculations for the metastable states of

\Pr^{9 +}

and

{Nd}^{10 +}

ions, systematically investigating their energy levels, transition properties, Landé

g_{J}

factors, and hyperfine interaction constants. Our results show excellent agreement with available experimental data and theoretical benchmarks, while resolving critical configuration assignment discrepancies through detailed angular momentum coupling analysis. The calculations highlight the significant role of Breit interaction and provide the first theoretical predictions of electric quadrupole hyperfine constants (

B_{hfs}

). These findings deliver essential atomic data for the development of next-generation optical clocks and establish lanthanide highly charged ions as exceptional candidates for precision tests of fundamental physics. Full article

(This article belongs to the Special Issue Atomic and Molecular Data and Their Applications: ICAMDATA 2024)

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18 pages, 2231 KiB

Open AccessArticle

Comparative DFT Study of K₂AgSbBr₆ and K₂NaScBr₆: Exploring the Role of B^′B^″ Cation Substitution on Material Properties

by Abdelkebir Ejjabli, Mohamed Karouchi, Hamza Errahoui, Abdelmounaim Laassouli, Aymane El haji, Youssef Lachtioui and Omar Bajjou

Atoms 2025, 13(6), 53; https://doi.org/10.3390/atoms13060053 - 13 Jun 2025

Abstract

The effects of cation substitution are the main emphasis of this investigation into the structural, mechanical, electronic, and optical properties of double perovskites K₂AgSbBr₆ and K₂NaScBr₆. Outwardly favorable tolerance and octahedral factors and negative formation energy [...] Read more.

The effects of cation substitution are the main emphasis of this investigation into the structural, mechanical, electronic, and optical properties of double perovskites K₂AgSbBr₆ and K₂NaScBr₆. Outwardly favorable tolerance and octahedral factors and negative formation energy confirmed structural stability and thermodynamic feasibility. Mechanical analysis showed that K₂AgSbBr₆ possesses greater volumetric stability and rigidity, while K₂NaScBr₆ exhibits greater ductility and isotropic characteristics. The electronic properties determined based on density functional theory (DFT) calculations indicate that K₂AgSbBr₆ has an indirect bandgap of 0.857 eV, making it suitable for applications using visible light, and K₂NaScBr₆ has a direct bandgap of 3.107 eV, making it ideal for UV-specific technologies. Optical analyses demonstrate complementary characteristics, particularly in terms of the dielectric function, absorption, reflectivity, energy loss function, refractive index, extinction coefficient, and optical conductivity. K₂AgSbBr₆ exhibits strong visible light absorptivity. Full article

(This article belongs to the Special Issue Ab Initio Calculations in Atomic, Molecular, and Optical Physics: A Tribute to Barry Irwin Schneider)

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12 pages, 532 KiB

Open AccessArticle

g-Factor Isotopic Shifts: Theoretical Limits on New Physics Search

by Dmitry S. Akulov, Rinat R. Abdullin, Dmitry V. Chubukov, Dmitry A. Glazov and Andrey V. Volotka

Atoms 2025, 13(6), 52; https://doi.org/10.3390/atoms13060052 - 13 Jun 2025

Abstract

The isotopic shift of the bound-electron g factor in highly charged ions (HCI) provides a sensitive probe for testing physics beyond the Standard Model, particularly through interactions mediated by a hypothetical scalar boson. In this study, we analyze the sensitivity of this method [...] Read more.

The isotopic shift of the bound-electron g factor in highly charged ions (HCI) provides a sensitive probe for testing physics beyond the Standard Model, particularly through interactions mediated by a hypothetical scalar boson. In this study, we analyze the sensitivity of this method within the Higgs portal framework, focusing on the uncertainties introduced by quantum electrodynamics corrections, including finite nuclear size, nuclear recoil, and nuclear polarization effects. All calculations are performed for the ground-state

1 s

configuration of hydrogen-like HCI, where theoretical predictions are most accurate. Using selected isotope pairs (e.g.,

{He}^{4 / 6}

,

{Ne}^{20 / 22}

,

{Ca}^{40 / 48}

,

{Sn}^{120 / 132}

,

{Th}^{230 / 232}

), we demonstrate that the dominant source of uncertainty arises from finite nuclear size corrections, which currently limit the precision of new physics searches. Our results indicate that the sensitivity of this method decreases with increasing atomic number. These findings highlight the necessity of improved nuclear radius measurements and the development of alternative approaches, such as the special differences method, to enable virtually the detection of fifth-force interactions. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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12 pages, 1058 KiB

Open AccessArticle

The Influence of External Radiation on the Emission Properties of H- and He-like Argon Ions in High Temperature Plasma

by Roman K. Kulikov, Igor Yu. Skobelev and Evgeny D. Filippov

Atoms 2025, 13(6), 51; https://doi.org/10.3390/atoms13060051 - 11 Jun 2025

Abstract

In the present work, the influence of external X-ray radiation on the kinetics of multicharged ions in high-temperature plasma is investigated. A generalized diagnostic approach is proposed for the electron density and temperature measurements of photo-pumped plasma based on the relative intensity of [...] Read more.

In the present work, the influence of external X-ray radiation on the kinetics of multicharged ions in high-temperature plasma is investigated. A generalized diagnostic approach is proposed for the electron density and temperature measurements of photo-pumped plasma based on the relative intensity of the H-like ion resonance line and its dielectronic satellites. Based on detailed kinetic calculations performed for argon plasma, the conditions under which these techniques can be applied without modification to the photo-pumped plasma are determined, and the relative intensities of these lines are calculated for cases where the external influence significantly alters the kinetics of their excitation. The development of such diagnostic methods is of particular importance for the experiments with powerful X-ray free-electron lasers and thermonuclear laser plasma. Full article

(This article belongs to the Special Issue Atom and Plasma Spectroscopy)

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1 pages, 128 KiB

Open AccessCorrection

Correction: Nishimura et al. Charge Exchange Spectroscopy of Multiply Charged Erbium Ions. Atoms 2023, 11, 40

by Yuki Nishimura, Saki Imaizumi, Hajime Tanuma, Nobuyuki Nakamura, Yuichiro Sekiguchi, Shinya Wanajo, Hiroyuki A. Sakaue, Daiji Kato, Izumi Murakami, Masaomi Tanaka and Gediminas Gaigalas

Atoms 2025, 13(6), 50; https://doi.org/10.3390/atoms13060050 - 9 Jun 2025

Abstract

The journal’s Editorial Office and Editorial Board are jointly issuing a resolution and removal of the Journal Notice linked to this article [...] Full article

10 pages, 509 KiB

Open AccessArticle

Energy Levels, Lifetimes, and Transition Properties for N iii – v

by Meichun Li, Juan Du, Kaijian Huang and Wenxian Li

Atoms 2025, 13(6), 49; https://doi.org/10.3390/atoms13060049 - 6 Jun 2025

Abstract

We present excitation energies, transition wavelengths, electric dipole (E1) transition rates, oscillator strengths, line strengths, and lifetimes for the 86 lowest states up to and including

1 s^{2} 2 s^{2} 7 f

in N iii, the 125 lowest states up [...] Read more.

We present excitation energies, transition wavelengths, electric dipole (E1) transition rates, oscillator strengths, line strengths, and lifetimes for the 86 lowest states up to and including

1 s^{2} 2 s^{2} 7 f

in N iii, the 125 lowest states up to and including

1 s^{2} 2 s 7 f

in N iv, and the 53 lowest states up to

1 s^{2} 8 g

in N v using the multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) methods. The computed results are then compared with data from the Atomic Spectra Database of the National Institute of Standards and Technology (NIST-ASD), experimental results, and other theoretical studies. For all levels in N iii – v, the root mean square energy differences from the NIST values are 130, 103, and 6 cm⁻¹, respectively. Compared to previous multiconfiguration Hartree–Fock and the Breit–Pauli (MCHF-BP) calculations, 89.3%, 98.5%, and 100% of the

log (g f)

values for N iii – v agree within 5%, respectively. Full article

(This article belongs to the Special Issue Atomic and Molecular Data and Their Applications: ICAMDATA 2024)

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13 pages, 1934 KiB

Open AccessArticle

Collision Kinematics for Fast Positron Impact Ionization of Argon

by Robert D. DuBois and Károly Tőkési

Atoms 2025, 13(6), 48; https://doi.org/10.3390/atoms13060048 - 4 Jun 2025

Abstract

Classical trajectory Monte Carlo calculations for 1 keV positron impact ionization of argon are presented. A combination of energy-weighted triple differential cross-sections is shown to provide good to excellent agreement compared with experimental data, depending on the ejected electron azimuthal angular acceptance range [...] Read more.

Classical trajectory Monte Carlo calculations for 1 keV positron impact ionization of argon are presented. A combination of energy-weighted triple differential cross-sections is shown to provide good to excellent agreement compared with experimental data, depending on the ejected electron azimuthal angular acceptance range used to define in-plane scattering. For ejected electron energies less than 100 eV, information about the influence of pre- (the impact parameter) and post-(the direction of scattering) collision kinematics on the triple differential level is obtained. An overall picture of these kinematic properties is also presented for single differential cross-sections as a function of ejected electron energy and ejection angle. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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